A seminal vesicle is a paired accessory gland that contributes fluid to semen. Its secretion includes fructose and other substances that help form the environment in which sperm are transported. The gland's duct joins the sperm-carrying pathway near the prostate.[ref]
Human Reproductive Anatomy and Gametogenesis. Section 43.3, male reproductive structures and accessory glands
Despite its name, a seminal vesicle is not primarily a storage sac for sperm. Sperm production, maturation, movement through ducts and addition of accessory-gland fluid are distinct contributions to reproduction. This distinction also explains why semen volume and sperm count describe different quantities: much of the ejaculated fluid is glandular secretion rather than sperm cells themselves.
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